JcTI-PepI, a synthetic peptide bioinspired in the trypsin inhibitor from Jatropha curcas, presents potent inhibitory activity against C. krusei, a neglected pathogen.

Antimicrobial resistance has been increasing globally, posing a global public health risk. It has prompted the scientific community to look for alternatives to traditional drugs. Antimicrobial Peptides (AMPs) have stood out in this context because they have the potential to control infectious diseases while causing no or little harm to mammalian cells. In the present study, three peptides, JcTI-PepI, JcTI-PepII, and JcTI-PepIII, were designed and tested for antimicrobial activity based on the primary sequence of JcTI-I, a 2S albumin with trypsin inhibitory activity from Jatropha curcas. JcTI-PepI strongly inhibited C. krusei growth, and it caused severe disruptions in cellular processes and cell morphology. C. krusei cells treated with JcTI-PepI showed indicative of membrane permeabilization and overproduction of Reactive Oxygen Species. Moreover, the yeast's ability to acidify the medium was severely compromised. JcTI-PepI was also effective against pre-formed biofilm and did not harm human erythrocytes and Vero cells. Overall, these characteristics indicate that JcTI-PepI is both safe and effective against C. krusei, an intrinsically resistant strain that causes serious health problems and is frequently overlooked. It implies that this peptide has a high potential for use as a new antimicrobial agent in the future.

Machaerium acutifolium lectin alters membrane structure and induces ROS production in Candida parapsilosis.

Lectins are a group of widely distributed and structurally heterogeneous proteins of nonimmune origin. These proteins have the ability to interact with glycans present on cell surfaces and elicit diverse biological activities. Machaerium acutifolium lectin (MaL) is an N-acetyl-D-glucosamine-binding lectin that exhibits antinociceptive activity via transient receptor potential cation channel subfamily V member 1 (TRPV1). Lectins that have the ability to recognize and interact with N-acetyl-D-glucosamine residues are potential candidates for studies of fungicidal activity. In this work, we show that MaL has antifungal activity against Candida species, and we describe its mode of action towards Candida parapsilosis. MaL inhibited the growth of C. albicans and C. parapsilosis. However, MaL was more potent against C. parapsilosis. The candidacidal mode of action of MaL on C. parapsilosis involves enhanced cell permeabilization, alteration of the plasma membrane proton-pumping ATPase function (H+-ATPase), induction of oxidative stress, and DNA damage. MaL also exhibited antibiofilm activity and noncytotoxicity to Vero cells. These results indicate that MaL is a promising candidate for the future development of a new, natural, and safe drug for the treatment of infections caused by C. parapsilosis.

RcAlb-PepII, a synthetic small peptide bioinspired in the 2S albumin from the seed cake of Ricinus communis, is a potent antimicrobial agent against Klebsiella pneumoniae and Candida parapsilosis.

Antimicrobial peptides (AMPs) are important constituents of the innate immunity system of all living organisms. They participate in the first line of defense against invading pathogens such as viruses, bacteria, and fungi. In view of the increasing difficulties to treat infectious diseases due to the emergence of antibiotic-resistant bacterial strains, AMPs have great potential to control infectious diseases in humans and animals. In this study, two small peptides, RcAlb-PepI and RcAlb-PepII, were designed based on the primary structure of Rc-2S-Alb, a 2S albumin from the seed cake of Ricinus communis, and their antimicrobial activity assessed. RcAlb-PepII strongly inhibited the growth of Klebsiella pneumoniae and Candida parapsilosis, and induced morphological alterations in their cell surface. C. parapsilosis exposed to RcAlb-PepII presented higher cell membrane permeabilization and elevated content of reactive oxygen species. RcAlb-PepII also degraded and reduced the biofilm formation in C. parapsilosis and in K. pneumonia cells. Experimentally, RcAlb-PepII was not hemolytic and had low toxicity to mammalian cells. These are advantageous characteristics, which suggest that RcAlb-PepII is safe and apparently effective for its intended use and has great potential for the future development of an antimicrobial agent with the ability to kill or inhibit K. pneumoniae and C. parapsilosis cells.

ClTI, a Kunitz trypsin inhibitor purified from Cassia leiandra Benth. seeds, exerts a candidicidal effect on Candida albicans by inducing oxidative stress and necrosis.

Cassia leiandra is an Amazonian plant species that is used popularly for the treatment of mycoses. Recently, a protease inhibitor, named ClTI, with insecticidal activity against Aedes aegypti, was purified from the mature seeds of C. leiandra. In this work, we show that ClTI has antifungal activity against Candida species and describe its mode of action towards Candida albicans. This study is relevant because the nosocomial infections caused by Candida species are a global public health problem that, together with the growing resistance to current drugs, has increased the urgency of the search for new antifungal compounds. ClTI inhibited the growth of Candida albicans, Candida tropicalis, Candida parapsilosis, and Candida krusei. However, ClTI was more potent against C. albicans. The candidicidal mode of action of ClTI on C. albicans involves enhanced cell permeabilization, alteration of the plasma membrane proton-pumping ATPase function (H+ -ATPase), induction of oxidative stress, and DNA damage. ClTI also exhibited antibiofilm activity and non-cytotoxicity to mammalian cells. These results indicate that ClTI is a promising candidate for the future development of a new, natural, and safe agent for the treatment of infections caused by C. albicans.

ClCPI, a cysteine protease inhibitor purified from Cassia leiandra seeds has antifungal activity against Candida tropicalis by inducing disruption of the cell surface.

Infections caused by Candida tropicalis have increased significantly worldwide in parallel with resistance to antifungal drugs. To overcome resistance novel drugs have to be discovered. The objective of this work was to purify and characterize a cysteine protease inhibitor from the seeds of the Amazon rainforest tree Cassia leiandra and test its inhibitory effect against C. tropicalis growth. The inhibitor, named ClCPI, was purified after ion exchange and affinity chromatography followed by ultrafiltration. ClCPI is composed of a single polypeptide chain and is not a glycoprotein. The molecular mass determined by SDS-PAGE in the absence or presence of ß-mercaptoethanol and ESI-MS were 16.63 kDa and 18.362 kDa, respectively. ClCPI was stable in the pH range of 7.0-9.0 and thermostable up to 60 °C for 20 min. ClCPI inhibited cysteine proteases, but not trypsin, chymotrypsin neither alpha-amylase. Inhibition of papain was uncompetitive with a Ki of 4.1 × 10-7 M and IC50 of 8.5 × 10-7 M. ClCPI at 2.6 × 10-6 M reduced 50% C. tropicalis growth. ClCPI induced damages and morphological alterations in C. tropicalis cell surface, which led to death. These results suggest that ClCPI have great potential for the development of an antifungal drug against C. tropicalis.